SDL_Quit man page

SDL_Quit shuts down all SDL subsystems and frees the resources allocated to them. This should always be called before you exit. For the sake of simplicity you can set SDL_Quit as your atexit call, like:

SDL_Init(SDL_INIT_VIDEO|SDL_INIT_AUDIO);
atexit(SDL_Quit);
.
.

Note:

While using atexit maybe be fine for small programs, more advanced users should shut down SDL in their own cleanup code. Plus, using atexit in a library is a sure way to crash dynamically loaded code